#include<stdio.h>
int main()
{
    int a;
    int b;
    int c;
    int d;
    while(~scanf("%d%d",&a,&b))
    {
        if(a==0&&b==0)
        {
            break;
        }
        printf("%d\n",a+b);
    }
    while(~scanf("%d%d",&c,&d))
    {
        printf("%d\n",c-d);
    }
    return 0;
}